Phenol is a basic commodity chemical with many end uses. Most of the phenol manufactured is prepared from isopropylbenzene, hereafter referred to as cumene. The reaction sequence is short and entails the following steps:
1. Air oxidation of cumene to give cumene hydroperoxide. ##STR1##
2. Acid cleavage of the hydroperoxide to provide phenol and acetone. ##STR2##
The phenol and acetone are separated and each one purified to the degree necessary to satisfy its ultimate use. As is readily observed, for every mole of phenol that is produced, a mole of acetone is also theoretically produced. Acetone is also a commodity chemical with various end uses. Although not shown in the schematic equations, there are by-products formed as well which must be removed to various degrees depending upon the end use of the phenol or acetone. Additionally other materials are introduced into the process to remove trace quantities of materials which may be deleterious to the products. One of these materials is water. It is usually introduced into the processing stream in the form of aqueous or slurried sodium hydroxide and is used to precipitate out the sulfate anion. As shown in the second equation above, the cleavage reaction is catalyzed by trace quantities of sulfuric acid. However, if the sulfuric acid remains in the processing stream, charring of products can occur. Therefore the sulfuric acid must be removed. This is usually done by contacting the reaction product of the cleavage reaction with aqueous or slurried sodium hydroxide in a vessel usually called a neutralizer. The sulfuric acid is neutralized and the sodium sulfate removed, usually as a dense aqueous solution. However, some of the water remains in the organic processing stream since it is soluble therein to a certain extent. Because of its relatively low boiling point it becomes associated with the low boiling acetone fraction distillate as opposed to the high boiling phenol fraction distillate. Under conventional acetone processing, the water is separated from the acetone in the final distillation tower as bottoms, the distillate acetone ready for sale in the market place. This final separation of water from acetone is very important since the product specification of commercial grade acetone should have no more than 0.5 wt. percent water. The less water in acetone, the higher is the quality of the product. Low water content acetone can command a higher price in the market place.
A new process for removing water from the acetone stream present in the sulfuric acid catalyzed cleavage of cumene hydroperoxide has been discovered. This process reduces the quantity of energy expended in separating acetone from water in the conventional processing. Furthermore, a final acetone purification column of substantially smaller size can now be employed. A product acetone with significantly reduced water content can be efficiently produced using the process of this invention.